Satellite positioning systems (SPS) such as the Global Positioning System (GPS) provide position location capabilities in mobile devices, and typically provide accurate results in outdoor environments. However, SPS signals may not be reliably received in attenuated signal environments, such as indoor or dense urban environments. In these environments different positioning techniques may be used to enable localization of mobile devices. For example, a position fix for a mobile device may be computed by measuring ranges to terrestrial transmitters (e.g., cellular base stations or wireless access points) and then performing trilateration or another range-based positioning technique. In another example, a position fix may be computed by weighting the locations of terrestrial transmitters based on signal strength measurements received at the mobile device. However, such localization techniques may suffer from poor accuracy and/or the need for specialized device hardware.